Part 1. Definition
In this task, you're given a context passage, followed by a question that needs to be answered. Based on the paragraph, you must write unambiguous answers to the questions and your answer must refer to a specific phrase from the paragraph. If multiple answers seem to exist, write the answer that is the most plausible.
Part 2. Example
Tracy slept awkwardly on their new bed and was having some pain, so Tracy cracked her neck. 
Question: What did Tracy do with her neck?
Answer: crack her neck
Explanation: The output phrase perfectly answers the question and is explicitly mentioned in the passage as well.
Part 3. Exercise
In fact , so much so , that the lines contained large chunks of yeast and protein . And it wasn't just my unfiltered - Belgian - beer line . The lines for Stella Artois and Miller Lite , if not chunky , were also filthy . I told the owner that he needed to clean his draft beer lines , and pronto . 
Question: Why did the lines contain large chunks of yeast and protein ?
Answer:
Because the lines were dirty .